Digital Subscriber Line (DSL) is a family of technologies used to provide digital data transmission over a local telephone network. By sending signals over the telephone line at high frequencies, DSL can transform an ordinary telephone line (e.g., twisted-pair) into a broadband communications link.
Over the years, DSL technology has evolved into a family of specific implementations and standards. These various implementations offer a variety of transmission speeds and transmission distances and include, for example, High Speed DSL (HDSL), Symmetrical or Single Pair DSL (SDSL), Symmetric High Speed DSL (SHDSL), Asymmetric DSL (ADSL), Very High Speed DSL (VDSL), and Rate Adaptive DSL (RADSL). The various DSL implementations that have evolved over the years may be collectively referred to as xDSL.
In contrast to some other communications protocols, DSL does not have the capability, at the physical layer (PHY) or the Transmission Convergence (TC) Layer, to signal a far-end transmitter to restrict or temporarily halt transmission of data when a near-end receiver becomes temporarily congested with information that it cannot forward to the intended destination. This situation often arises when the destination is busy with other tasks or is processing previously received data and therefore is not ready to receive information from the near-end receiver's TC layer. Because the far-end transmitter is often continually sending data to the near-end receiver, the receiver's TC data buffers can overflow, forcing the receiver to drop the information until the intended destination is able to accept the data from the TC layer.
The dropped information is lost, and this loss is usually detected at a higher layer, such as a web browser application, which forces a retransmission of the original data. Because detection of lost information is done at a higher layer, and because there is significant latency involved in getting information to the higher layer, this retransmission can cause a significant reduction in data transfer at the application layer.
What is needed are systems and methods for a near-end receiver to control the far-end transmitter's data transmission such that the near-end receiver's TC data buffers do not overflow.
Features and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.